1. Field of the Invention
The present invention relates to a development apparatus for performing development using a two-component developer composed of toner and carrier, a process cartridge having the development apparatus, and an image forming apparatus with this development apparatus or process cartridge, such as an electrophotographic copying machine, printer, plotter, facsimile machine, or complex machine with a combination of these machines. The present invention further relates to an image forming apparatus having a plurality of the development apparatuses or process cartridges and capable of forming color images.
2. Description of the Related Art
As a development apparatus of a biaxially-conveying type that performs development using a two-component developer, there has conventionally been known a configuration in which two developer conveying members (screws, augers, or the like) and two conveying paths are disposed substantially in a horizontal direction below a developer supporting body (a developing roller, a sleeve, or the like), one of the developer conveying members (screws, augers, or the like) being used for supplying and recovering a developer to and from the developer supporting body, while the other one being used for conveying and stirring the developer after toner is replenished, and one of the conveying paths being a supplying/recovering conveying path, while the other one being a stirring/conveying path.
In such a biaxially-conveying type development apparatus, the toner density of the developer within the development apparatus spatially fluctuates due to replenishment of toner or consumption of toner (development). For this reason, reduction of fluctuation of the toner density was conventionally performed by diffusing the developer by means of the developer conveying members (screws, augers, or the like). In order to improve the diffusion capacity of the developer conveying members such as screws, the number of rotations of the screws can be increased or the shape of the screws can be changed creatively by attaching fins or the like. However, there is a limit to such ideas, thus the developer cannot be diffused sufficiently before reaching the developer supporting body (a developing roller, a sleeve, or the like), whereby the toner density fluctuation may still be observed in the developer drawn up to the developer supporting body.
Therefore, there has been proposed in, for example, Examined Utility Model Application Publication No. H6-6380 a development apparatus of a biaxially-conveying type in which, in order to reduce the toner density variation occurring in the axial direction of the developer supporting body, a plurality of opening sections are provided on a partition plate (partition wall) provided between two screws, and a guide member that inclines to the partition plate in a developer conveying direction and guides a developer to the opening members is also provided.
In the conventional development apparatus with the biaxial configuration, the developer does not flow divergingly on the developer conveying members (e.g., screws), whereby the waveforms of the toner density fluctuation that are formed on the screws due to toner replenishment or consumption are kept as is. Then, only the amplitude of the waveforms are reduced by means of stirring/conveying using the screws while keeping the waveforms, thus it is necessary to cause the developer to circulate within the development apparatus a number of times until the amplitude of the waveforms becomes vanishingly small.
The conventional technology described in the above Examined Utility Model Application Publication No. H6-6380 is intended to reduce the variation occurring in the axial direction of the sleeve of the biaxial development apparatus, and has the opening sections on the partition plate, but does not control the phase of the toner density fluctuation. Specifically, in order to achieve the above object, it is essential that the developer flows from the screw, which is far from the sleeve, to the screw on the sleeve side via the opening sections, thus it is necessary to cause the developer to circulate within the development apparatus a number of times until the amplitude of the waveforms becomes vanishingly small.